The invention relates to a fixing element for fixing insulating strips or plates and optionally additional sealing strips on a solid substructure.
Such fixing elements, as well as their availability in a preassembled state, are already known in many varied configurations. In a preassembly of the fixing elements, the screws are inserted in the fixing elements. Then, the fixing elements are processed by means of automatic setting machines, in which a screwdriver bit directly provides the axial advance of the screw as well as the insertion of the fixing element into a roofing strip.
In relatively small roofing structures or during the fixing of insulation strips or plates, it is desirable that the fixing elements be pre-inserted by hand in a preassembled state, i.e. pushed by hand into the insulating strips or plates and optionally into additional sealing strips. Such pushing-in can also be advantageous when it is followed by processing with a setting machine.
One embodiment of the fixing element of the present invention is adapted for use with a screw which is provided with a thread over at least a portion of the length of its shaft and which has a screw head. The fixing element preferably includes a large-surface area washer having a tubular extension that defines a passage for receiving the screw. The tubular extension includes at least one rib to preferably allow the fixing element and screw to be pushed into insulation.
The object of the present invention is to substantially improve the handling potential during pre-insertion of a fixing element of the previously described kind.
In accordance with the invention, this is achieved by providing, in the segment of the tubular extension for axially displaceable reception of the screw head, at least one rib which protrudes radially inward into the displacement region, or one or more burls or the like, against which the screw head can abut after surmounting the ribs, burls or the like in a direction which is opposite to that of the screwing-in direction toward the free end of the tubular extension.
The screws are preassembled in a tubular extension of the large-area washer by pushing-in the screw head past an appropriate obstacle (rib, burl or the like), whereby the rib, burl or the like forms an abutment for pushing the completed fixing element into insulating strips or plates and potentially also into sealing strips. Due to the large-area washer, there is available a relatively large hand-hold for mounting the fixing element, and that is so independently of whether insertion is by hand or by means of a setting tool, so that the force transfer, during pushing into the insulating strips or plates and optionally additionally into sealing strips, can be carried out without any problem. Nevertheless, there is the assurance that the screw cannot move all the way into the tubular extension, but rather encounters a limiting member in the form of a rib, a burl or the like. Even with relatively forceful pushing-in of the preassembled fixing element, the force exerted upon the large-area washer is transmitted by the rib, burl or the like to the screw head and thereby to the inserted screw. This also ensures that the boring or penetrating tip formed at the free end of the screw always lies at the most forward point of the preassembled fixing element, whereby the pre-insertion of the fixing elements is facilitated.
One kind of embodiment contemplates that the rib, burl or the like is formed near the mid-range of the length of the tubular extension. By so doing, the screw can slide axially inside the tubular extension over a relatively wide range, which creates a telescopic effect. A telescopic effect is especially appropriate for use of the fixing element in the roof area, i.e. when walk-on surfaces are to be provided with such fixing elements. When stepping on such a fixing element, the large-area washer with the tubular extension can move downwardly in the axial direction and then back again into the initial position, through the elastic action of the insulating strips or plates.
A preferred embodiment is one in which there is provided an annular rib extending around the entire inside wall. In a preassembly, this rib can not be easily surmounted, because the preassembly of large-area washers having tubular extensions and screws is usually performed with appropriate assembly tools which provide the required force. If the fixing elements are then pre-inserted by hand, there exists the assurance that the screw head can no longer surmount the complete annularly closed rib, i.e. a firm abutment exists.
It is preferable that the spacing of the rib, burl or the like from the free end of the tubular extension is less than the overall length of the screw including a boring portion formed at its free end. This provides assurance that, in the condition in which the screw head abuts against the rib, burl or the like, the free end of the screw and especially its boring portion still always protrudes beyond the free end of the tubular extension. This substantially facilitates penetration by the fixing element during pre-insertion.
It also contributes to simple mounting capability and optimal abutting during pre-insertion, if the screw head is lens-shaped and its transition to the shaft has a truncated cone shape. In such a case, it is possible during preassembly to easily push the screw head over the projecting rib, burl or the like. Nevertheless, the lens-shaped configuration of the top of the screw head assures an optimal abutment.
The configuration of the preassembled fixing elements, in accordance with the invention, creates the additional possibility that several washers having a tubular extension which are contiguous to each other, or which follow each other closely, are connected to each other by webs or tapes into a kind of screw strip. This makes it substantially easier for transportation and pre-insertion at the construction site. In this connection, the joined-together washers can also be made so as to be relatively easy to separate from each other.
In theory, it is conceivable that the respective screws can be mounted in the tubular extension of the washers just before pre-insertion. Preferably, however, the screws are already preassembled in the tubular extensions of the large-area washers, i.e. each screw head is already pushed in past the rib, burl or the like at the internal limit of the tubular extension, so that the rib, burl or the like serves as abutment for the screw head. By such preassembly, loss prevention is additionally provided, because both during transportation and during their use at the construction site, the screws can not fall out of the tubular extensions of the large-area washers.